Solar-powered, soda can furnaces help heat homes

By Anthony Cotton, The Denver Post

Posted:
01/09/2014 12:37:46 AM MST

Updated:
01/09/2014 12:37:51 PM MST

University professor Aaron Brown and Metro students instal a solar powered soda can furnace in a Denver home. The project is a joint project between the University of Colorado, Boulder, and the community non-profit Revision International. (Kathryn Scott Osler/The Denver Post)

Aaron Brown has built water heaters for schools in Costa Rica and done charity work all around the world. But the Metropolitan State University of Denver professor says some of the most rewarding work he's ever done is happening in a Denver neighborhood.

“You don't have to go to far off places to help people — there are plenty of things to do right here,” Brown said about the Westwood neighborhood. “With this project you feel a lot more rewarded and you see a direct, very local benefit.”

Brown, who teaches mechanical engineering at Metro State, is working with students and a local nonprofit to build solar powered furnaces for homes in the neighborhood. With empty soda cans as one of the main parts of the design, the furnaces cost around $30 to make and are expected to save about the same amount in monthly energy costs.

Anderson said the electricity used by the fans costs about two cents a day. Cool air is drawn into the unit's base and then heated as it travels up through drilled holes in the 144 aluminum cans, which have been heated by the sun. The air then exits through ventilation holes at the top of the unit. While there has to be a supplemental source of heat at night, the units reach up to 170 degrees during the day. One unit, installed in November, heated a room from 60 degrees to 90 degrees in 20 minutes.

It's possible to “upgrade” the units — spending another $20 for an acrylic cover, $2 for a thermostat or $2.50 for a shower curtain to drape around it — but that almost defeats the purpose of providing reliable and inexpensive energy, Brown said.

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University of Colorado Boulder students first created a $60 furnace, but Brown thought the price could be lowered. He challenged his Metro State students to make faster, cheaper, and more efficient and reliable units.

“You have to be really creative,” said Richard Anderson, a Metro State senior who's part of the project team. “Right now, the unit will last for about a winter without any maintenance. If you bumped up the cost to about $100, it would last three or four times longer. But you're talking about soda cans and computer fans that you can buy six for $10 on eBay and you're supplying heat to an entire house.”

Two heaters were installed in homes in November, and most installations are scheduled for later this month.

“There was a little boy who was going to be sleeping there. He was going, 'I'm going to be so warm tonight,'” Anderson said. “That was just so cool — it's really exceeded my expectations.”

The success tempered some neighbor's initial skepticism. Even though the idea of inexpensive heat came from area residents, there were doubts that the unattractive, simple contraptions would actually work.

Brown and Joseph Teipel, director of operations and co-founder of partner non-profit Revision International, held a series of meetings in the community. Although Revision International had previous successes in areas like backyard gardens and urban farms, some people were still leery.

“[You're] talking about soda cans being glued together, so it's not something that just comes to people's minds,” Teipel said. “But the initial installations were key. Now that they've seen it and see how well it works, they're really excited.”

Brown said there's no reason why the project can't spread beyond Colorado. He's already talked with people in Chicago and recently corresponded with a woman who's connected to refugee camps in Syria.

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